Scale-up purification of previously described recombinant HIV-1 and HIV-2 env polypeptides have been achieved by a protocol which we have developed for obtaining milligram quantities of apparently homogeneously pure 566, 566 delta, 318, 569 (HIV-1) and 996 (HIV-2) polypeptides, respectively. Several milligram quantities of the highly purified immunogenic gp4l polypeptide 566 and its C-terminal truncated analog 566 delta, as well as the highly immunogenic HIV-2 gp35 polypeptide 996, have been purified and made available to our collaborators for evaluation as sensitive HIV-1 and HIV-2 diagnostic reagents and for design of potential subunit anti-HIV vaccines. We are also utilizing many of the purified env polypeptides for epitope mapping studies with human anti-env antibodies. In addition, many antigenic sites on the HTLV-I gp46 and gp2l env glycoproteins have also been identified using previously expressed recombinant polypeptides, and their reactivity with antibodies in sera from ATL, TSP, and healthy (HTLV-I carriers) individuals were studied. We showed that the C-terminus of gp46 (recombinant env polypeptides RP-B plus RP-C) is the most immunogenic region of the HTLV-I env reactive with human positive sera.